Echinodermata

A phylogeny can help us do lots more than simply study evolutionary history. It also helps us know what traits are shared by different but related groups of organisms. 1: Multicellular 2: Land plants 3: Vascular plants 4: Seed plants 5: Symmetry and tissues 6: Bilateral symmetry, coelom, and nervous system 7: Deuterostome development 8: Molting of exoskeletons 9: Trochophore larva

Adults exhibit pentaradial symmetry, but the larvae are bilaterally symmetrical Echinoderms are considered deuterostomes, anus formed first Lack cephalization, have few sensory organs Have 2 sides: oral-the side with the mouth, aboral-the side without the mouth

The water vascular system aids in locomotion, feeding, attachment, respiration Water enters through the madreporite and moves through the organism to the arms and tube feet Tube feet fill with water and help the organism grab surfaces and pull themselves along Some species have regenerative tissue, they can re-grow limbs

Class: Crinoidea Sea lilies and feather stars This class attaches to a substrate with a stalk Appx 700 extant species

Class: Asteroidea Sea stars Arms radiate from a central disc, but are not distinct from it Madreporite and anus are on aboral side Move with tube feet

Class: Ophiuroidea Brittle Stars Their flexible arms branch from a small central disc Madreporite is on oral side Mouth and anus are the same opening The aboral surface of the disc is protected by plates called sheilds

Class: Echinoidea Sea urchins and sand dollars and sea biscuits Most are free moving but some bore into rock Tube feet bring food into their mouths Their teeth are arranged into a structure known as Aristotle’s Lantern

Class: Holothuroidea Sea cucumbers When threatened, they can expel their intestines, which are regenerated later